The present invention is generally related to control of internal combustion engines, and, more particularly, the present invention is related to system and method for synchronizing engine speed in boats equipped with multiple engines.
Reciprocating internal combustion engines may create high acoustical noise and vibration during operation. Particularly in the case of vessels equipped with paired engines as their primary propulsion device, it is desirable to run such vessels with each engine operating synchronized relative to one another, that is, each engine should operate at the same or nearly the same speed. Lack of engine synchronization may cause annoying beat frequencies that would result in annoying discomfort to the occupants of the vessel. Under some known techniques, the engine synchronization may be attempted by manual adjustment of the throttle levers at the helm of the vessel. At best such techniques may only be partly effective since they may require human intervention, such as helmsman's observation of engine speed meters, e.g., tachometers, in conjunction with manual adjustment of the throttle levers. Under such techniques, the occupants of a multi-engine vessel with engines running at cruising speeds are often subjected to unpleasant noise and transmission and/or engine vibration when the respective speed or revolutions per minute (rpm) of the two or more propulsion engines are not held very close to one another, that is, when the engines are not synchronized.
As will be understood by those skilled in the art, most modern relatively large marine engines for pleasure boats and other marine vessels may be operated from a helm station using remote engine controls with throttle and shift engine control inputs conveyed to the engine by mechanical push-pull cables. Unfortunately, even relatively minor variations in control mechanisms, control cables, control cable routing, and engine throttle control linkages, and the adjustments thereof can collectively result in substantial differences in mechanical efficiency between the remote control lever and the engine's input signal device. Thus, in the case of known automated synchronizers, since these synchronizers generally rely on mechanically adjusting the respective throttle levers and throttle valves and associated cabling, these automated synchronizers tend to be expensive and unaffordable in small boat applications and subject to the above-described difficulties of having to provide mechanical control to a relatively inaccurate system. Engine control may be further complicated by routine engine operations, such as rotation of the engine about its steering axis or tilting (trimming) of the engine about its tilt axis, which operations can also affect mechanical throttle input to the engine's input signal device.
In view of the foregoing issues, it should be appreciated that remote control of throttle lever position by controlling lever or handle position relative to the other, either manually or automatically, can become unwieldy since such levers may become substantially offset relative to one another or have unpredictable relative position and often do not provide equal throttle control input and fail to provide appropriate engine synchronization even though the levers may be physically adjacent to one another. Thus, it is desirable to overcome the disadvantages of presently available remote engine control systems and to accurately synchronize engine speeds by utilizing microprocessor-based system and techniques to compare engine speeds and adjust engine power output electronically, thus achieving accurate and reliable engine synchronization by electronically controlling engine power independent of the respective primary throttle control input signal supplied to each engine.